Hi,
I can recommend the TomTom Go series of units. I use the base model myself, the 300. The models above this, the 500 & 700 have bluetooth, which means they can interface to your phone. I think this gives a hands-free facility to your phone but you'll have to check.
I'm very happy with mine. You can pre-plan journeys and navigate between postcodes or places. There isn't anything it doesn't do, for me anyway. You may have special requirements however.
Not being able to get a GPS lock can be caused by heating elements in some windscreens having a shielding effect on the unit. A plug-in antenna is available if this is a problem in your car.
There are many review sites on the web but I find that looking at amazon.co.uk is often quicker when comparing units and reading users comments.